Sawmill apparatus

ABSTRACT

Apparatus including a horizontally movable carriage slidably supported by a track. A hydraulic cylinder and piston therefor are mounted on the carriage below the track. A fixed clamp is carried by the cylinder and a hinged clamp is mounted on the piston rod with both clamps projecting above the track. The carriage is reciprocated to feed a log, the ends of which are engaged by the two clamps, past cutting elements which straddle the track and clear the clamps. As the empty carriage is returned to the starting position, the hinged clamp folds beneath a preloaded log and later is moved towards the fixed clamp so that the log is gripped therebetween.

Apr. 8, 1975 3,459,246 8/]969 Ottosson..,...............,.H... l44/3l2 R 3,736,968

[ SAWMILL APPARATUS FOREIGN PATENTS OR APPLICATIONS Inventors: Norman E. Noble, North Vancouver. British Columbia;

Leflwld Boehm; West meow/fir l60.9()7 l0/l957 l44/209 British Columbia, both of Canada Primary Examiner-Donald R. Schran gent, or FirmFethcrstonhaugh & Co,

A h. w m r m Nn m mu m @d r m mm V LU 0 ac vn 0a NV a e n m s s A M 7 Canada [57] ABSTRACT Apparatus including a horizontally movable carriage [22] Filed: Sept. 26, 1973 Appl. No.1 400,821

slidably supported by a track. A hydraulic cylinder and piston therefor are mounted on the carriage below the track. A fixed clamp is carried by the cylinder and a hinged clamp is mounted on the piston rod with both clamps projecting above the track. The carriage is reciprocated to feed a log, the ends of which are engaged by the two clamps, past cutting elements which straddle the track and clear the clamps. As the empty carriage is returned to the starting position, the hinged References Cned clamp folds beneath a preloaded log and later is UNITED STATES PATENTS 8/l902 (1/1964 'l/l966 moved towards the fixed clamp so that the log is gripped therebetweens 707 184 Thomas 81/425 2 3,138.17) Bretlldgcr .r 83/4351 2 242 954 Schikofsky...i...4................. 83/425 2 9 Clam, 5 Drawmg F'gum PATENTEUAPR 8l975 SHEET 3 Bf 4 SAWMILL APPARATUS Our invention relates generally to sawmill equipment for producing lumber and more particularly to apparatus for feeding a log to a saw in a manner which ensures speedy and accurate cutting.

A conventional sawmill carriage normally is a wheeled structure mounted on a track and designed to support a log as it is fed to a saw. The log is clamped to the carriage by some sort of clamping or dogging mechanism as it is commonly called and this mechanism generally grips the log near the top and bottom surfaces with the mechanism being positioned to one side of the log so as to clear a vertically disposed saw. This arrangement allows a cut to be made longitudinally of the log on the side thereof opposite the dogging mechanism whereupon the carriage must be returned to the starting position to allow the log to be repositioned and redogged for the next cut. The procedure is time consuming and otherwise unsatisfactory since the sawyer may have difficulty in correctly positioning the log prior to dogging with the result that a greater-thanusual amount of wood will be wasted.

Attempts have been made to overcome this problem by providing means for holding a log with some other clamping arrangement such as one which grips the outer surface of the log from below so that wood can be removed from the upper portion of the log but this too has its disadvantages. It is recognized that an ideal way to grip the log is by means of clamping members applied to the ends of the log much in the same manner a cylindrical work piece is chucked in a lathe. One known attempt to clamp the ends of a log in this manner requires the use of an overhead guiding arrangement for the clamping members. This makes it difficult to avoid side play or flexure of the log and it is absolutely essential that the log be firmly held if accurate cutting is to be achieved. Furthermore, a log cannot be loaded onto the equipment while the log previously placed on the carriage is being cut and this slows down production of the sawmill.

Our sawmill apparatus provides a wheelless carriage which is slidably mounted on a track and is fitted with upwardly projecting clamps which can be applied to the ends of the log supported just clear of the top surface of the track. The carriage construction is such that the log is rigidly held and extremely accurate cutting is possible. As the carriage is being moved past the saw during the last cut to be made on a log or cant. another log can be loaded onto the machine and can be properly positioned awaiting the return run of the carriage, thus affecting a saving in operating time with a resulting increase in production over a given period. This is achieved by making one of the end clamps foldable so that the empty carriage can be moved beneath a preloaded log which subsequently is properly clamped prior to being advanced to the saw. The clamping arrangement allows the use of twin band saws which can be arranged to cut simultaneously from opposite sides of the log and furthermore the spacing between the cutting runs of the saws can be reduced to a minimum so that a series of board-producing cuts are possible without releasing and repositioning the log on the carriage.

In drawings which illustrate a preferred embodiment of the invention,

FIG. 1 is a schematic perspective view of sawmill apparatus constructed in accordance with the present invention.

FIG. 2 is an enlarged vertical section taken on the line 2-2 of FIG. 1,

FIG. 3 is an enlarged longitudinal section of the apparatus with parts being shown in elevation, and

FIG. 4 is a plan showing a log positioning mechanism of the apparatus, and

FIG. 5 is an enlarged transverse section taken on the line 5-5 of FIG. 4.

Referring to the drawings, the numeral indicates generally sawmill apparatus which forms the basis of the present invention.

As shown in FIG. I, the apparatus 10 comprises a track 12 which is straddled by a bandmill 14. A carriage 16 runs along the track and is provided with clamps l8 and 20 designed to grip the end of a log L. Drive means 22 serves to reciprocate the carriage through a cutting stroke and a return stroke whereby to feed the clamped log to the mill l4 and withdraw the sawn log prior to another cut. The logs are individually moved into a position to be loaded on the carriage, by a mechanism 24 near one end of the track 12. Slabs and/or boards 26 which are sawn from the log are moved laterally away from the track down a lumber deck 28.

Referring now to FIGS. 1, 2 and 3, the track 12 is shown mounted on a base 30 formed of pedestals 31, 32 and 33. Track 12 is made up ofa pair of rails 36 and these vertically standing rails rest on horizontally disposed bed plates 37 which are spaced apart to provide a longitudinally extending and centrally disposed slot 38. This slot 38 connects a guideway 39 defined between the transversely spaced rails 36 with a longitudinal passageway 40 formed by the transversely spaced apart pairs of pedestals 31, 32 and 33.

In FIGS. 2 and 3, the carriage generally indicated at 16 will be seen to comprise an elongated slide beam 44 which is slidably mounted in the guideway 39 between the rails 36 so as to rest on the bed plates 37. The beam 44 is rectangular in cross-section (FIG. 2), the beam being longer than the longest log likely to be cut by the apparatus. Such an arrangement ensures that the beam is firmly held between the guide rails 36 so that it cannot flex along its considerable length or move laterally as it travels back and forth along the track. The beam 44 has a through bore 45 which is also rectangular in cross-section and slidably mounted in this bore is a close-fitting slide bar 46 which is also firmly supported against all movement except endwisemovement within the beam. An integrally formed bracket 47, see FIG. 3, is provided intermediate the length of the slide bar 46, which bracket projects downwardly through a longitudinal slot 48 formed in bottom wall 49 of the box-like beam 44.

The slide bar 46 is adapted to be moved lengthwise of the beam 44 by a fluid-operated mechanism generally indicated at 50. As shown best in FIG. 3, the mechanism 50 comprises a hydraulic cylinder 51 which is fitted with a piston rod 52. Opposite ends of this lengthy cylinder 51 are secured to the beam 44 by means of depending brackets 54 and 55 which project downwardly through the slot 48 so that the mechanism 50 is sup ported for travel within the passageway 40 and in the same vertical plane as the carriage beam 44. Thus, when opposite ends of the cylinder SI are selectively pressurized, the slide bar 46 is caused to move lengthwise of the beam 44.

Fluid for pressurizing the cylinder 51 is developed by means generally indicated at 60 and which is shown in FIG. 3 only. The fluid pressure means 60 is mounted on a narrow platform 61 which is secured by brackets 62 and 63 to the underside of the elongated slide beam 44 near one end thereofand the bracket 54 supporting the cylinder 51 whereby to travel back and forth in the passage 40. Means 60 comprises an electric motor 64 for driving a pump 65, a reservoir tank 66 and a solenoid operated valve 67. All these parts are interconnected by a suitable circuit generally indicated at 68 and part of which extends to opposite ends of the cylinder 51. The motor 64 and valve 67 are controlled by a circuit generally indicated at 70, a portion of which is shown in FIG. 3. The circuit 70, of course, includes a flexible conduit (not shown) connecting the means 60 to a source ofelectric power whereby the carriage is free to travel back and forth without interference.

Above the cylinder 51, the clamp 18 is fixedly secured to top wall 75 of the slide beam 44. This up' wardly projecting clamp 18 is a narrow, metal plate which may not be more than 2 inches wide and it has a vertical side edge 77 provided with horizontally pro jecting teeth 78.

Opposite the fixed clamp 18, the narrow clamp 20, which has a side edge 81 provided with similar teeth 82, projects upwardly through a longitudinal slot 84 formed in the beam wall 75. A horizontal hinge pin 86 is mounted on the slide bar 46 to extend transversely of a slot 87 formed therein and the lower end of the clamp 20 is mounted on this pin whereby said clamp can swing towards and away from the clamp 18 in a common vertical plane extending through the center of the carriagev The hinged clamp 20 is provided with a stop 88 which is adapted to bear on the upper surface of the slide bar 46 when the side edge 81 of the clamp is vertical. A spring 89 connects the clamp 20 to the bracket 47 on the piston rod whereby to bias the clamp to the upright position shown by solid lines in FIG. 3.

The clamps 18 and 20 can be spaced apart to grip a log which may be some 20 feet or more in length. It will be noticed in FIG. 3 that the slide beam 44 is considerably longer than the maximum length of any log likely to be handled by the apparatus and that the two clamps are always well spaced from the opposite ends of the slide beam. This ensures that even a large diameter and heavy log is properly supported by the carriage 16 with the log being reasonably well balanced. The slide beam 44 in turn is supported by the track 12 so that it cannot flex along its considerable length and thus the log can be advanced to the saw or saws without wavering so as to cause an inaccurate cut.

The drive means generally indicated at 22 and shown best in FIG. 1 comprises a winding drum 94 which is positioned directly below the track so that the axis of rotation of the drum is at right angles to the longitudinal axis of the track. A reversible electric motor 95 is provided to drive the drum and this motor is included in the control circuit 70. Wound around the drum 94 is a cable 96. One end of this cable extends off the drum and is trained around sheaves 97 and 98 mounted between the pair of pedestals 31. The end of this portion ofthe cable is secured to one end of the slide beam 44 as shown at 99 in FIG. 3. The other end of the cable 96 extends off the drum 94 and is trained around sheaves 102 and 103 journalled between the pairs of pedestals 33 supporting the opposite end of the track, this cable end being secured as at 104 (FIG. 3) to an adjoining end of the slide beam. Thus, when the drum 94 is rotated by the motor 95, first in one direction and then in the other direction, the carriage 16 is caused to travel back and forth along the track 12. The carriage 16, of course, starts its cutting stroke from a position adjoining the log positioning mechanism 24 and terminates that stroke at the lumber deck 28 with the return stroke being between the deck and the mechanism. Band mill 14 is located a suitable distance in between these two extreme positions of the carriage and the cutting stroke is such that a log 20 feet or more in length may be processed by the present apparatus.

The log positioning mechanism which is generally indicated at 24 is shown best in FIGS. 4 and S as being positioned alongside a deck across which logs are moved sideways by means of a suitable conveyor, not shown. Logs are transferred from the deck 120 to a position above the track 12 by mechanically operated log stop and loader arms 121. Since the arms 121 are of conventional design, detailed description is not considered necessary but, briefly, these vertically disposed arms are longitudinally spaced along the track 12 and are pivotally mounted as at 122. Each arm 121 is pivoted by means of an air cylinder and piston rod arrangement 123 which is mounted on a base 124 for the mechanism 24. Thus, the arms 121 can be rocked in one direction to form a stop for a log coming off the deck 120 then be rocked in the other direction to transfer the log onto the track 12.

When the log is rolled off the arms 121, it is received by a pair of centering rolls 126 which are spaced one on each side of the track 12. These suitably ribbed rolls 126 are carried by mounting means 128 comprising pairs of arms 129 which are pivoted on the base 124 as at 130. The longitudinally spaced pairs of arms 129 support the rotatably mounted rolls 126 so that they can be swung in an arcuate path towards and away from the center of the track 12 as well as above and slightly below the top edge of said track. A preferred operating means 132 for moving the rolls 126 in the aforesaid manner comprises air cylinders and their piston rods which are both indicated at 133, the cylinders being mounted on the base 124 as shown in FIG. 5. Arms 129 of each pair are interconnected by stabilizers 134 which keep the rolls 126 equidistantly spaced from the center of the track at all times.

Drive means generally indicated at 138 is provided for rotating the rolls 126 either towards or away from each other, see FIG. 4. Preferably, the means 138 comprises a hydraulic motor 139 for each roll with an interconnecting drive train 140 therebetween. These motors 139 are of the variable-speed, reversible, and freerunning type.

The mechanism 24 is provided with opposing pairs of support arms which are arranged in rows, one row on each side of the track 12. A preferred mounting means 147 for each arm 145 comprises a crank 148 which pivotally connects said arm to the base 124. Each pair of arms is interconnected by an elongated stabilizing bar 149. The mounting and stabilizing arrangement enables the arms 145 to be moved substantially horizontally towards and away from the center of the track by operating means 150. FIG. 5 shows the operating means 150 to comprise an air cylinder 151 which connects each arm 145 to an adjacent upright 152 on the frame 124. The inner or unsupported end of each support arm 145 projects through an annular groove 154 formed in an adjacent roll 126. Thus, the rolls 126 can swing in an are from a widely spaced position where they are entirely blow the uppermost edges of the support arms 145 to a closely spaced position where the rolls project slightly above said edges of the arms.

Finally, the log positioning mechanism 24 comprises a guide fence 160 which extends parallel to the axis of the track 12 on the side thereof opposite the log stop and loader arms 121. The horizontally movable fence 160 is selectively adjustable towards and away from the center of the track 12 by means generally indicated at 162. As shown best in FIG. 5, the means 162 comprises a suitable number of longitudinally spaced air cylinders 163 which are mounted on a frame member 164 with the piston rods 165 of said cylinders being operatively connected to the fence.

The present apparatus is adapted to be controlled by a sawyer or operator who mans an operating console (not shown) located directly above and a short distance away from the mechanism 24. This console has a panel provided with electric switches or the like for controlling all the various movements of the apparatus which are required to reduce a log to boards. The bandmill 14 is also controlled by the operator through conventional setworks, also not shown. By way of example, the mill 14 is shown as comprising a pair of bandmills 14a arranged to provide two vertical cutting runs 1411 which can be spaced apart a minimum of 4 inches. The setworks provides this minimum as well as other spacings of the runs 14b whereby boards of varying thickness can be sawn from a passing log. Finally, the single operator has control over the several operating parts which make up the mechanism 24.

Briefly, the operation of the apparatus 10 is as follows: the carriage 16 is moved to the loading end of the structure and the clamp 18 and 20 are moved apart a distance greater than the length of the log which is being moved up into position by the mechanism 24. Mechanism 24 is manipulated to position the log exactly in the center of the track whereupon the clamps are moved together to grip opposite ends of the log. The bandmill 14 is adjusted to place the cutting runs 14b in a position which will cut boards from the logs of the required thickness. The carriage 16 is then moved to pass the log between the cutting runs of the bandsaws whereby to saw boards or slabs from opposite sides of the log, the boards or slabs falling on to the lumber deck 28 and being carried away for further processing. On the return stroke of the carriage 16, the bandsaws are moved apart to allow the cant now being gripped by the clamps to pass freely between the cutting runs. The spacing between the cutting runs is then reset and the cutting operation is repeated.

More specifically, the operation of the mechanism 24 allows a log to be placed gently on the rolls 126 which are placed close together to receive the logs, the support arms 145 being widely spaced apart to avoid contact with the log. The rolls 126 are rotated by the drive means 138 to revolve the log to the best possible or selected position for sawing whereupon the clamps 18 and 20 are operated to grip the log ends. The carriage 16 is rolled along the track whereby the bandmill 14 will cut slabs from opposite sides of the passing log.

This reduces the log to a flat-sided structure commonly referred to as a cant which is indicated by the letter C in FIG. 5. The cant is moved by the carriage on its return stroke past the saws and back to the loading position where the clamps 18 and 20 are moved apart to release the cant. Normally the cant will fall onto one of its flat sides although the mechanism 24 may be operated for this purpose if necessary. The support arms carry the cant at this time and the guide fence and/or the rolls 126 are brought into play to center the cant between the clamps l8 and 20 which are then reapplied to chuck' or grip the log. When this is done. the bandmill 14 is adjusted to trim the uncut sides of the cant during the cutting stroke of the carriage. The now squared-off timber is returned to allow resetting of the bandmill which subsequently will cut boards of the required thickness when the apparatus is suitably controlled by the sawyer.

When the carriage l6 eventually arrives at the lum ber deck 28 after the last cutting stroke, the clamps l8 and 20 are moved apart to release the lumber slab so that it may fall onto said deck. In the meantime, another log is moved into position by operation of the mechanism 24. The carriage is returned to pick up this preloaded log and, when the hinged clamp 20 strikes the end of the log, it folds down into the slot 84 so as to pass beneath the log and in sliding contact therewith. Clamp 20 is snapped to its normally upright position by the spring 89 when said clamp passses beneath the opposite end of the log whereupon the mechanism 50 can be operated once again to clamp the ends of the log.

From the foregoing, it will be apparent the sawmill apparatus 10 can be operated to quickly and accurately saw a log into boards. Preloading of the log helps to speed up the operation but it will be noted two (or more if additional saws are provided) cuts can be made during each cutting stroke. The invention contemplates the use of chipper heads which would be used with the twin bandmill 14, the heads being applied to the sides of the log during the first cutting stroke to remove side slabs in the form of chips in accordance with the preferred procedure in some sawmills. Logs of various lengths and diameters as well as mishapen logs can be readily handled by the present apparatus since the car riage is supported and guided from a position below the log in a manner which ensures precision cutting regardless of the log size.

We claim:

1. Sawmill apparatus comprising a track formed of a pair of guide rails, a carriage slidably mounted between the guide rails for endwise movement lengthwise of the track away from and towards a log-loading position near one end of said track. a fluid-operated mechanism mounted on the carriage below the track and including an extensible member, a fixed clamp movable with the carriage and projecting upwardly between the rails, a hinged clamp operatively connected to the extensible member for swinging movement about a horizontal axis extending across the track and projecting upwardly between the rails longitudinally spaced from and in substantially the same vertical plane as the fixed clamp, stop means for supporting the hinged clamp in a generally upright position whereby to limit swinging movement away from the fixed clamp, spring means biasing the hinged clamp toward the upright position, means for supplying pressurized fluid to the fluid-operated mechanism whereby to apply the clamps to opposite ends of a log positioned above the track in the logloading position, and drive means for reciprocating the carriage through a cutting stroke and a return stroke relative to a cutting element disposed intermediate the length of the track and in close proximity to the path of travel of the clamps whereby to cut the clamped log lengthwise, said hinged clamp passing beneath a preloaded log as the empty carriage completes a return stroke whereby automatically to snap upwardly for engagement with an end of said preloaded log.

2. Sawmill apparatus as claimed in claim 1. in which said hinged clamp is operatively connected to the extensible member by a bar slidably mounted on the carriage for endwise movement longitudinally of said carriage.

3. Sawmill apparatus as claimed in claim 1, in which said carriage comprises an elongated slide beam having a bore and a length greater than the maximum length of any log to be cut. said extensible member being an elongated slide bar slidably mounted in the bore of the slide beam.

4. Sawmill apparatus as claimed in claim 1, and including a log positioning mechanism near an end of the track operable to center a log in the common vertical plane of the clamps and to adjust the log vertically a selected distance above the track, said log positioning mechanism including a pair of centering rolls disposed one on each side ofthe track to extend parallel thereto, mounting means rotatably supporting the rolls for swinging movement towards and away from the center of the tracks as well as above and below a top edge of said track. operating means for selectively positioning the rolls with respect to the track, and drive means for rotating the rolls either towards or away from one an other.

5. Sawmill apparatus as claimed in claim 4. and including a plurality of support arms arranged in row disposed one row on each side of the track, mounting means supporting each row of support arms for substantially horizontal movement towards and away from the center of the track. operating means for selectively positioning the rows or support arms with respect to the track. said support arms projecting through annular grooves formed in the pair of centering rolls and cooperating with said arms to manouver a log into the required position to be gripped between the clamps.

6. Sawmill apparatus as claimed in claim 5, and including a guide fence mounted alongside the track, and means for selectively adjusting the guide fence towards and away from the center of the track.

7. Sawmill apparatus comprising a track formed of a pair ofguide rails. a carriage slidably mounted between the guide rails for endwise movement lengthside of the track, said carriage including a slide beam having a bore, a slide bar slidably mounted in the bore and projecting from one end of the slide beam, a fluid-operated mechanism below the track operatively connecting the slide beam to the slide bar whereby to extend and retract said slide bar, a fixed clamp mounted on the slide beam and projecting upwardly above the pair of guide rails, a hinged clamp mounted on the slide bar in opposition to the fixed clamp, spring means biasing the hinged clamp away from the fixed clamp, stop means limiting swinging movement of the hinged clamp away from the fixed clamp, means for supplying pressurized fluid to the fluid-operated mechanism whereby to apply the clamps to opposite ends of a log positioned above the track drive means for reciprocating the carriage through a cutting stroke and a return stroke relative to a cutting element disposed intermediate the length of the track and in close proximity to the path of travel of the clamps whereby to cut the clamped log lengthwise. and a log positioning mechanism near an end of the track operable to center a log in the common vertical plane ofthe clamps and to adjust the log vertically a selected distance above the track, said hinged clamp being adapted to fold beneath and travel lengthwise of a log supported by the log positioning mechanism and to again swing upright once clear of the log at the com pletion of the return stroke of the carriage.

8. Sawmill apparatus as claimed in claim 7, in which said log positioning mechanism includes a pair of centering rolls disposed one of each side of the track to extend parallel thereto, mounting means rotatably supporting the rolls for swinging movement towards and away from the center of the track as well as above and below a top edge of said track. operating means for selectively positioning the rolls with respect to the track, drive means for rotating the rolls either towards or away from one another. a plurality of support arms ar ranged in rows disposed one row on each side of the track, mounting means supporting each row of support arms for substantially horizontal movement towards and away from the center of the track, operating means for selectively positioning the rows of support arms with respect to the track. said support arms projecting through annular grooves formed in the pair of centering rolls and cooperating with said arms to maneuver a log into the required position to be gripped between the clamps.

9. Sawmill apparatus as claimed in claim 8, and including a guide fence mounted alongside the track, and

means for selectively adjusting the guide fence towards and away from the center of the track. 

1. Sawmill apparatus comprising a track formed of a pair of guide rails, a carriage slidably mounted between the guide rails for endwise movement lengthwise of the track away from and towards a log-loading position near one end of said track, a fluid-operated mechanism mounted on the carriage below the track and including an extensible member, a fixed clamp movable with the carriage and projecting upwardly between the rails, a hinged clamp operatively connected to the extensible member for swinging movement about a horizontal axis extending across the track and projecting upwardly between the rails longitudinally spaced from and in substantially the same vertical plane as the fixed clamp, stop means for supporting the hinged clamp in a generally upright position whereby to limit swinging movement away from the fixed clamp, spring means biasing the hinged clamp toward the upright position, means for supplying pressurized fluid to the fluidoperated mechanism whereby to apply the clamps to opposite ends of a log positioned above the track in the log-loading position, and drive means for reciprocating the carriage through a cutting stroke and a return stroke relative to a cutting element disposed intermediate the length of the track and in close proximity to the path of travel of the clamps whereby to cut the clamped log lengthwise, said hinged clamp passing beneath a preloaded log as the empty carriage completes a return stroke whereby automatically to snap upwardly for engagement with an end of said preloaded log.
 2. Sawmill apparatus as claimed in claim 1, in which said hinged clamp is operatively connected to the extensible member by a bar slidably mounted on the carriage for endwise movement longitudinally of said carriage.
 3. Sawmill apparatus as claimed in claim 1, in which said carriage comprises an elongated slide beam having a bore and a length greater than the maximum length of any log to be cut, said extensible member being an elongated slide bar slidably mounted in the bore of the slide beam.
 4. Sawmill apparatus as claimed in claim 1, and including a log positioning mechanism near an end of the track operable to center a log in the common vertical plane of the clamps and to adjust the log vertically a selected distance above the track, said log positioning mechanism including a pair of centering rolls disposed one on each side of the track to extend parallel thereto, mounting means rotatably supporting the rolls for swinging movement towards and away from the center of the tracks as well as above and below a top edge of said track, operating means for selectively positioning the rolls with respect to the track, and drive means for rotating the rolls either towards or away from one another.
 5. Sawmill apparatus as claimed in claim 4, and including a plurality of support arms arranged in row disposed one row on each side of the track, mounting means supporting each row of support arms for substantially horizontal movement towards and away from the center of the track, operating means for selectively positioning the rows or support arms with respect to the track, said support arms projecting through annular grooves formed in the pair of centering rolls and cooperating with said arms to manouver a log into the required position to be gripped between the clamps.
 6. Sawmill apparatus as claimed in claim 5, and including a guide fence mounted alongside the track, and means for selectively adjusting the guide fence towards and away from the center of the track.
 7. Sawmill apparatus comprising a track formed of a pair of guide rails, a carriage slidably mounted between the guide rails for endwise movement lengthside of the track, said carriage including a slide beam having a bore, a slide bar slidably mounted in the bore and projecting from one end of the slide beam, a fluid-operated mechanism below the track operatively connecting the slide beam to the slide bar whereby to extend and retract said slide bar, a fixed clamp mounted on the slide beam and projecting upwardly above the pair of guide rails, a hinged clamp mounted on the slide bar in opposition to the fixed clamp, spring means biasing the hinged clamp away from the fixed clamp, stop means limiting swinging movement of the hinged clamp away from the fixed clamp, means for supplying pressurized fluid to the fluid-operated mechanism whereby to apply the clamps to opposite ends of a log positioned above the track drive means for reciprocating the carriage through a cutting stroke and a return stroke relative to a cutting element disposed intermediate the length of the track and in close proximity to the path of travel of the clamps whereby to cut the clamped log lengthwise, and a log positioning mechanism near an end of the track operable to center a log in the common vertical plane of the clamps and to adjust the log vertically a selected distance above the track, said hinged clamp being adapted to fold beneath and travel lengthwise of a log supported by the log positioning mechanism and to again swing upright once clear of the log at the completion of the return stroke of the carriage.
 8. Sawmill apparatus as claimed in claim 7, in which said log positioning mechanism includes a pair of centering rolls disposed one of each side of the track to extend parallel thereto, mounting means rotatably supporting the rolls for swinging movement towards and away from the center of the track as well as above and below a top edge of said track, operating means for selectively positioning the rolls with respect to the track, drive means for rotating the rolls either towards or away from one another, a plurality of support arms arranged in rows disposed one row on each side of the track, mounting means supporting each row of support arms for substantially horizontal movement towards and away from the center of the track, operating means for selectively positioning the rows of support arms with respect to the track, said support arms projecting through annular grooves formed in the pair of centering rolls and cooperating with said arms to manouver a log into the required position to be gripped between the clamps.
 9. Sawmill apparatus as claimed in claim 8, and including a guide fence mounted alongside the track, and means for selectively adjusting the guide fence towards and away from the center of the track. 